Honda FourTrax Recon TRX250TM 2019, Owner'S Manual

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Technical Information 185
High Altitude Carburetor
Adjustment
At high altitude, the standard carburetor air-fuel mixture will be too
rich. Performance will decrease, and fuel consumption will increase.
A very rich mixture will also foul the spark plug and cause hard
starting. Operation at an altitude that differs from that at which this
engine was certified, for extended periods of time, may increase
emissions.
High altitude performance can be improved by specific modifications
to the carburetor. If you always operate your engine at altitudes
above 6,500 feet (2,000 meters), have your servicing dealer perform
this carburetor modification. This engine, when operated at high
altitude with the carburetor modifications for high altitude use, will
meet each emission standard throughout its useful life.
Even with carburetor modification, engine horsepower will decrease
about 3.5% for each 1,000-foot (300-meter) increase in altitude.
The effect of altitude on horsepower will be greater than this if no
carburetor modification is made.
NOTICE
When the carburetor has been modified for high altitude operation,
the air-fuel mixture will be too lean for low altitude use. Operation
at altitudes below 5,000 feet (1,500 meters) with a modified
carburetor may cause the engine to overheat and result in serious
engine damage. For use at low altitudes, have your servicing dealer
return the carburetor to original factory specifications.
19 TRX250TM-31HS0630.book Page 185 Thursday, April 5, 2018 3:37 PM